Generally, in a railroad vehicle (hereinafter “vehicle”), a main motor (hereafter “electric motor”) is loaded in the cart which is located under the body. The torque of this electric motor is transmitted to a wheel via a joint and a spur gearing, and is used to move the vehicle.
Extension of the maintenance cycle, i.e., the need for an electric motor with longer periods between the performance of maintenance, is increasing. In order to satisfy such needs, the development of a totally enclosed motor is desirable.
The structure of a totally enclosed motor is explained. The inner side of the circumference of a cylindrical frame is provided with a stator iron core, which has a stator coil in the totally enclosed motor. The bracket and housing, which comprise the sealing case, are attached to both ends of the frame. The bearing is respectively built in these brackets and the housing.
A rotor shaft extends through the sealing case, and both ends are supported by the bearings, enabling free rotation. A rotor iron core is attached to the central part of the rotor shaft, and it is located inside the stator iron core. A ventilation fan is attached to the rotor shaft within the sealing case. The labyrinth seal part is formed between a ventilation fan's peripheral part, and a bracket.
An inspiratory port is formed in the perimeter portion of the bearing of a bracket, the open air is led to a ventilation fan's center section from this inspiratory port, and it is discharged outside through the ventilation flue of a bracket.
For an electric motor composed in this way, the open air does not circulate inside of the apparatus, so the inside of apparatus is not soiled with dust. Therefore, the need to disassemble the apparatus so that the inside of electric motor can be cleaned is eliminated or reduced.
The electric motor includes a detection part which rotates with the rotor, and a speed sensor which detects the detection part in order to perform rotation control and vehicle brake control. These detection parts and the speed sensor are outside of the sealing case, and are covered by the cover for intercepting the open air.
Because the electric motor for a rail car is installed in the narrow attachment space of the cart, usually there are space restrictions. Therefore, when the speed sensor and detection part are attached to the outside of the sealing case (with the speed sensor and detection parts covered as described), the size of the axis of the electric motor (consisting of a stator iron core and a rotor iron core) becomes small. When the size of the axis of the electric motor becomes smaller, the output of the electric motor will decrease as a result.